I'm a huge fan of Doctor Who and particularly the stories written by Stephen Moffat. He loves the logical paradoxes that result from time travel and I would like to present one such scenario. The point of the thread is not to prove anything but is an interesting thought exercise.

Imagine for a moment that a man wants to kill a person who was responsible for the death of his father. However, he wants to kill the person before they get a chance to kill the father and thus change history. He builds a time machine and steals a samurai sword from his local museum. He leaves what is his present on 4th January 2008 and travels back to 6th August 2007. The journey results in his time machine completely breaking down and unfortunately he is killed by his father's killers in the attempt of killing them. The killers, in order to appear benevolent and rid themselves of the evidence, donate the sword (that appears very rare) to the local museum. This is the sword that is later stolen by the time traveler in an attempt to kill his father's murderers.

This results in what is called an ontological paradox. The sword has a beginning and an end in real time history. It arrives into history on 6th August 2007 when it is brought back from the future by the time traveler. It leaves history when it leaves 4th January 2008 to go back in time. Consequently, prior to 6th August 2007 it doesn't exist and after 4th January 2008 it doesn't exist. However, it is impossible that the sword was ever designed or created in anyway.

Whilst it appears that classical objects cannot exist in such paradoxical states it got me thinking about quantum states that do appear capable of such feats (called quantum superpositions). If the appearance of a particle was actually a particle coming from the future and the disappearance of the particle (some time after) was actually the particle slipping back through time then the particle would appear to have a beginning and end in real time yet it would be logically impossible for the particle to have been created.

it's stories like these that make my brain turn inside out. First of all say a guy goes into the past (before he was born) and accidentally kills his mother. Would that mean he never existed and it's impossible for anyone to do that, or would he cease to exist when he entered back into his own time, or would he continue to be in existence even up to when he was supposed to be "born"?

no need to get your grey cells in a knot coz it has been proved that travelling back in time is impossible, but travelling to the future is very,very possible.

Travel into the past is possible (theoretically speaking) for quantum states.

no,it isn't. Atleast that's what Stephen hawking said and that's the view of the majority of the scientific community.

No it is not . All of time exists co currently in space time. A quantum particle which exists in all places before being defined (as per the principle of quantum superposition) could travel in those points in the time stream which already exist. Google quantum mechanics, because it is different than normal physics.

After all, Stephen Hawking is #1 Who are we to argue with him?

Link? In any case I admit that normal objects such as a sword can not do this. We are discussing quantum mechanics. Learn more science newfag.

I'm a huge fan of Doctor Who and particularly the stories written by Stephen Moffat. He loves the logical paradoxes that result from time travel and I would like to present one such scenario. The point of the thread is not to prove anything but is an interesting thought exercise.

Imagine for a moment that a man wants to kill a person who was responsible for the death of his father. However, he wants to kill the person before they get a chance to kill the father and thus change history. He builds a time machine and steals a samurai sword from his local museum. He leaves what is his present on 4th January 2008 and travels back to 6th August 2007. The journey results in his time machine completely breaking down and unfortunately he is killed by his father's killers in the attempt of killing them. The killers, in order to appear benevolent and rid themselves of the evidence, donate the sword (that appears very rare) to the local museum. This is the sword that is later stolen by the time traveler in an attempt to kill his father's murderers.

This results in what is called an ontological paradox. The sword has a beginning and an end in real time history. It arrives into history on 6th August 2007 when it is brought back from the future by the time traveler. It leaves history when it leaves 4th January 2008 to go back in time. Consequently, prior to 6th August 2007 it doesn't exist and after 4th January 2008 it doesn't exist. However, it is impossible that the sword was ever designed or created in anyway.

Whilst it appears that classical objects cannot exist in such paradoxical states it got me thinking about quantum states that do appear capable of such feats (called quantum superpositions). If the appearance of a particle was actually a particle coming from the future and the disappearance of the particle (some time after) was actually the particle slipping back through time then the particle would appear to have a beginning and end in real time yet it would be logically impossible for the particle to have been created.

Thoughts?

We had a discussion before on the thread about God and free will. I basically played devil's advocate with Augustinian philosophy (mostly because I was bored of the typical responses in favor of free will), but we did wander a little into space-time when talking about the idea of "knowing decisions before they happen."

My question concerns itself with what you call "real-time history", without the hyphen.

no need to get your grey cells in a knot coz it has been proved that travelling back in time is impossible, but travelling to the future is very,very possible.

Travel into the past is possible (theoretically speaking) for quantum states.

no,it isn't. Atleast that's what Stephen hawking said and that's the view of the majority of the scientific community.

No it is not . All of time exists co currently in space time. A quantum particle which exists in all places before being defined (as per the principle of quantum superposition) could travel in those points in the time stream which already exist. Google quantum mechanics, because it is different than normal physics.

After all, Stephen Hawking is #1 Who are we to argue with him?

Link? In any case I admit that normal objects such as a sword can not do this. We are discussing quantum mechanics. Learn more science newfag.

sorry for offending you, oh high and mighty king of CR. I was a commerce student back at school because science bored the snot out of me.